The present invention relates to rechargeable batteries for electronic devices and, in particular, to reducing battery overheating probability during charging of the rechargeable batteries.
Many electronic devices such as cellular phones include a rechargeable battery as a power source for the device. The battery is typically charged by connecting the phone to a charger. During the charging operation, the temperature of the battery will normally increase because some of the electrical inputs, such as the charge current, are converted to heat within the battery cells (see FIG. 1). Overheating of the battery, however, decreases charging efficiency and can cause battery damage (see FIG. 2). Battery temperature is thus a critical parameter in the charging process.
Overheating during charging can be caused by various factors. For example, overheating may be caused by the designs of the hardware charging circuit, the charging algorithm, software control process, or charging accessories. The technical designs may be refined to prevent potential overheating problems. In addition to searching for better technical methodologies, a simple solution can be used to improve air circulation during charging and reduce the probability of battery overheating.
Typically, rechargeable batteries may contain a built-in thermistor, and the battery temperature can be monitored directly by the control software during charging. In this regard, the charging process is pulsed or aborted if the battery temperature increases above a charging temperature limit. However, the product costs could be significantly reduced by removing the built-in thermistor. In this context, battery temperature has to refer to the device ambient temperature. Since these two temperature measurements lack correlation, however, it is difficult to accurately and promptly detect battery overheating, and charging control is more challenging. If the battery temperature increases without detection by the control components, overheating could result.